Mahmoud Moradi, Giray Enkavi, and Emad Tajkhorshid.
Atomic-level characterization of transport cycle thermodynamics in
the glycerol-3-phosphate:phosphate transporter.
Nature Communications, 6:8393, 2015.
(PMC: PMC4598623)
MORA2015-ET
Membrane transporters actively translocate their substrate by undergoing large-
scale structural transitions between inward- (IF) and outward-facing (OF) states
(‘alternating-access’ mechanism). Despite extensive structural studies, atomic-
level mechanistic details of such structural transitions, and as importantly, their
coupling to chemical events supplying the energy, remain amongst the most
elusive aspects of the function of these proteins. Here we present a quantitative,
atomic-level description of the functional thermodynamic cycle for the glycerol-
3-phosphate:phosphate antiporter GlpT by using a novel approach in
reconstructing the free energy landscape governing the IF
OF
transition along a cyclic transition pathway involving both apo and substrate-
bound states. Our results provide a fully atomic description of the complete
transport process, offering a structural model for the alternating-access
mechanism and substantiating the close coupling between global structural
transitions and local chemical events.
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